While he recovers from multiple injuries sustained during the 49ers-Steelers game in December, Manuel Austin Jr. has started a campaign and a website called EndFanViolence.com. He heartily supports a bill that would bar convicted assailants from attending professional sporting events in California.

But the person cited as his attacker has not been convicted and therefore is not affected by the bill. In fact, none of the five most prominent incidents involving Bay Area sports teams has resulted in a conviction, and only one has led to formal charges. The bill is, in effect, icing for a cake still in search of an oven.

The legislation would be difficult to enforce even if the perpetrators could be definitively identified - a big hurdle, if Austin's case is any indication. Based on the police response immediately after the attack, Austin concedes, he might have been targeted for the ban list himself.

The 66-year-old Los Gatos man says police originally handcuffed and interrogated him, bloodied and missing several teeth, for more than an hour after the incident. He said he and three accompanying family members finally convinced them that he was the victim, not the perpetrator. The case, as originally reported in The Chronicle three months ago, became a he-said, he-said debate, and Austin said Thursday that investigators have been unable to find independent witnesses.

State Assemblyman Mike Gatto, a Democrat from Los Angeles, introduced the sports-violence legislation last month, primarily in response to the beating of Giants fan Bryan Stow in a Dodger Stadium parking lot on Opening Night last year. Stow celebrated his 43rd birthday last month, in a wheelchair and living at the Santa Clara Valley Medical Center. He moved to a rehabilitative facility last week.

His alleged assailants have not gone to trial yet, and they could legally attend the home opener at Dodger Stadium next month. If they are convicted, Gotto's bill would require that their names and photos be published in a database for five years and sent to stadiums or arenas, ticket vendors and police agencies. If caught at a game, they would be charged with a misdemeanor. If they caused more mayhem at a game, they'd face a year behind bars and a $10,000 fine.

But if it's difficult to find and prosecute miscreants after they cause bodily harm in a large crowd, how will they be apprehended for simply walking into a stadium with tickets purchased by a friend? Or showing up after an event to create chaos in the parking lot, where Stow was attacked and where two men were shot in separate incidents at Candlestick Park after a 49ers-Raiders preseason game in August?

Neither of the shootings has been solved. Nor has a rest-room beating that sent a man to the hospital on the same night. Lt. Jim Miller of the city's gang task force said one of the two shooting victims stopped cooperating and declined to look at pictures of a possible suspect. A suspect was arrested shortly after the shootings but was released soon after and never charged. Miller called the case open but inactive.

The restroom beating has led to similar dead ends. Lt. Chris Pedrini of the criminal investigations unit said the victim has stayed in touch with the department and that attempts to find incriminating video from surveillance cameras outside the restroom did not produce conclusive evidence.

Austin said the assault that knocked out four teeth and left him with a concussion occurred after the first of two infamous power outages at the Monday night game with the Steelers. In this age of multipurpose phones, it's hard to believe that no one caught the incident on camera.

The best element of Gatto's bill would establish rewards for whistleblowing fans. The rest of it seems like a gesture, though not entirely futile. Professional teams have a vested interest in assuring fan safety, but too often, they get away with dismissing periodic assaults as aberrations, well below the level of violence to be expected in a gathering of up to 70,000 excitable people.

If Gatto's grandstanding counters that spin, he's done a service. This week, news reports of the bill drew a little more attention to the campaign by Austin, who has stayed in touch with prosecutors and an investigating officer and written to 49ers owner Jed York.

Austin has pretty grand visions. He can imagine a world in which violence of any kind at a sporting event results in a cancellation of the game, no refunds for the patrons. That would certainly motivate ticket holders to look out for each other.

The idea seems far, far ahead of its time. This one seems more reasonable. If you were at Candlestick that night and you saw a fight just before the start of the game, call the San Francisco police. Existing laws should be enough to control this problem.